X ray questions:What material is suitable in windows for hard X-rays?

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SUMMARY

The discussion focuses on suitable materials for windows and reflective coatings for hard X-rays, specifically at 200 eV. For this energy level, a free-standing silicon nitride (SiN) membrane on a silicon frame is recommended due to its low absorption and ability to withstand radiation damage. For higher energy levels, materials such as Beryllium and CVD diamond are appropriate for X-rays above 3.5 keV, while aluminum, plastics, and silicon wafers are suitable for hard X-rays above 20 keV. A naked silicon mirror is optimal for 200 eV due to its excellent quality and large critical angle.

PREREQUISITES
  • Understanding of X-ray energy levels and their implications on material selection
  • Familiarity with materials like silicon nitride (SiN), Beryllium, and CVD diamond
  • Knowledge of radiation damage effects on materials
  • Basic principles of X-ray optics and reflectivity calculations
NEXT STEPS
  • Research the properties and applications of silicon nitride (SiN) membranes in X-ray optics
  • Explore the use of Beryllium and CVD diamond for X-ray applications above 3.5 keV
  • Learn about the critical angle and reflectivity calculations for X-ray mirrors
  • Investigate the resources available at the Center for X-Ray Optics for transmission and reflectivity data
USEFUL FOR

Researchers, physicists, and engineers working in X-ray optics, materials science, and radiation applications will benefit from this discussion.

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What material is suitable in windows for hard X-rays?

What material would you choose as reflective coating of X-rays mirrors for radiation at 200 eV? Why?
 
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Hmm, 200 eV is very very soft. The only window you can use for that is a free-stainding SiN membrane one a Si frame (substrate with a small window etched into it). These are commercially available, up to maybe a few window mm size.

A window is always a compromise of thickness and the material's absorption length. The latter depends on Z. Generally speaking you want Z as low as you can get, but the material has to withstand possible radiation damage.

For x-rays above 3.5keV or so you can use Beryllium (Z= 4 for large pieces) or CVD diamond (Z=6 for smaller pieces). For hard x-rays above 20keV or so you can use Al, plastics or even Si wafers.

For 200 eV I would use a naked Si mirror without any coating. The critical angle at 200 eV is large enough, and Si you can get in excellent quality.

Check out the Center for X-Ray Optics. There you can calculate transmission and reflectivity of softish X-rays.

http://henke.lbl.gov/optical_constants/
 

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